Characteristics and driving factors of soil fauna communities in reclaimed grasslands of coal mines across different elevations in the Qilian Mountains, China

Understanding the recovery of soil fauna communities in reclaimed mining areas is essential for evaluating the ecological effectiveness of restoration practices in alpine ecosystems. However, the combined effects of altitudinal gradients and soil physicochemical filters on soil fauna assembly during the early stages of coal mine reclamation remain poorly understood. Here, we investigated soil fauna communities across altitudinal gradients (2260–3070 m) in the Gansu Qilian Mountain Nature Reserve, integrating linear mixed-effects models (LMM), non-metric multidimensional scaling (NMDS), permutational multivariate analysis of variance (PERMANOVA), similarity percentage (SIMPER) analysis, hierarchical partitioning (HP), and Bayesian structural equation modeling (BSEM) to disentangle the direct and indirect drivers of community composition and diversity. Our results revealed that A total of 41 families from 15 orders were identified, with Hymenoptera and Coleoptera dominant. LMM revealed a significant altitude × reclamation interaction on activity density and taxonomic richness. PERMANOVA showed altitude as the primary community driver. Diversity indices showed no significant differences between reclaimed and natural sites at equivalent elevations. Hierarchical partitioning identified total phosphorus (24.85%), sand (13.00%), and pH (12.15%) as the top environmental predictors, while BSEM indicated that altitude influenced fauna indirectly through soil properties, with electrical conductivity exerting a direct positive effect (β = 0.62). Our findings demonstrate that reclamation promotes partial recovery of soil fauna, with several community-level metrics converging toward natural reference levels, although full restoration has not been achieved. Recovery outcomes are strongly elevation-dependent, emphasizing the need for altitude-specific management strategies in alpine mining regions.